Mechanisms Of Stress: A Dynamic Overview Of Hormonal And Behavioural Homeostasis

Stress has been found difficult to provide a distinct definition, however it has been defined by most studies as most circumstances that people would find stressful. Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychological bulletin, 130(4), 601) and it is a subjective experience for each individual. It has also been referred to as “a state of threatened homeostasis”.

There is theory that suggests that a system referred to as the GAS (General Adaptation Syndrome) model is a general response to any stressor that may be present. When a stressor is present, the brain activates either the anterior pituitary gland or the sympathetic nervous system as a response to the stress. Hormones such as Catecholamine secretion are increased in response to stress. Cortisol is also released through activation from the pituitary-adrenal. One theory aimed their study on potential mechanisms that are responsible for the changes in cardiovascular responsiveness, endocrine and immune responses to acute psychological stress. Their results confirmed that aspects of physiological functions were affected by psychological stressors.

There has been research that has also focused on many aspects of stress responses. One study has focused on cortisol response to a psychological stressors. The study focused on the effects of nicotine on the release of cortisol in response to the participants self-administrating nicotine. When the stressful procedure was present, results showed that there was an increase in cortisol levels at a significant level in response to the stress. There has also been recent research that has focused on. This type of study is important as it can assist with future research by providing an insight on system activation and hormonal changes in response to stress. Therefore, the aim of this study was to examine the effect of stress (public speaking) on subjective, cardiovascular and hormonal responses. It was hypothesized that La Trobe students studying Behavioural Neuroscience B who participated in public speaking would display higher cardiovascular response (systolic and diastolic blood pressure and heart rate), increased endocrine response (cortisol levels in saliva) and higher subjective levels of stress after (experiment) the presentation in comparison to their levels before the presentation (baseline). 135 first year behavioural neuroscience psychology students participated in this study. Materials used for this study was a Professional Blood pressure Machine HBP-130, a Salivette® cortisol code blue. A subjective stress rating. Recorded using a single item. Scale was between 1 and 9 asking what their level of stress is at the present moment. 1 was minimal level of stress and 9 was maximum level of stress.

Participants had given the experimenter a subjective rating of stress (scale from 1-9) to complete prior to the experiment, they also had their heart rate and blood pressure (systolic and diastolic) using a Professional Blood pressure Machine HBP-130. Cortisol levels were also recorded prior to the public speaking task using the Salivette® cortisol code blue, to provide with baseline levels. Immediately after public speaking task was completed, the participants would retake a subjective rating scale, have their blood pressure and heart rate taken again when they would be considered to be experiencing ‘high stress’. Also, cortisol levels were taken 20 minutes after their presentation (due to time needed for activation of endocrine system to respond to stress present).

Results

An independent-samples t-test was conducted to compare stress levels for public speaking and no public speaking conditions. Subjective Stress Rating, Systolic Blood Pressure, Diastolic Blood Pressure, Heart Rate and Cortisol levels were recorded. For Subjective Stress Rating (SSR), the difference was significant as the baseline scores were (M = 3. 75, SD = 1. 89) and the experimental scores were (M = 5. 88, SD = 1. 99). conditions; t (268) = 9. 049, p = 0. These results can suggest that there is a significant change in stress perception as Figure 1 below shows a significant increase between the baseline and experimental. Figure 1: Mean change (+1. 99) in Subjective Stress Rating in Response to the Public Speaking Exercise. For Systolic Blood Pressure (SysBP), the difference was significant as the baseline scores were (M = 126. 59, SD = 19. 41) and the experimental scores were (M = 131. 30, SD = 17. 91). conditions; t (268) = 2. 073, p = 0. 39. These results can suggest that there is a significant change in systolic blood pressure as Figure 2 below shows a significant increase between the baseline and experimental. For Diastolic Blood Pressure (SysBP), the difference was not significant as the baseline scores were (M = 71. 87, SD = 12. 57) and the experimental scores were (M = 73. 79, SD = 10. 56). conditions; t (268) = 1. 358, p =. 176.

These results can suggest there is no significant change in diastolic blood pressure, however, there is still a slight increase in diastolic blood pressure, it only displays a minor increase between the baseline and experimental. For Heart Rate (HR), the difference was not significant as the baseline scores were (M = 77. 00, SD = 15. 36) and the experimental scores were (M = 86. 42, SD = 15. 94). conditions; t (268) = 4. 945, p =. 00. These results can suggest that there is a significant change in Heart rate, as shown in figure 4 below, it shows a major increase between the baseline and experimental. For Heart Rate (HR), the difference was not significant as the baseline scores were (M = 77. 00, SD = 15. 36) and the experimental scores were (M = 86. 42, SD = 15. 94). Conditions; t (268) = 4. 945, p =. 00. These results can suggest that there is a significant change in Heart rate, as shown in figure 4 below, it shows a major increase between the baseline and experimental.

Discussion

The aim of the experiment was to examine the effect of stress (public speaking) on subjective, cardiovascular and hormonal responses. As expected, there was an increase in heart rate, systolic and diastolic blood pressure which is shown from figure 2, 3 and 4 above displaying increases between the baseline and experimental. There was also an increase in cortisol levels and subjective stress rating. Overall, these results support the hypothesis that students who participated in public speaking would display higher cardiovascular response (blood pressure and heart rate), increased endocrine response (cortisol levels in saliva) and higher subjective levels of stress after (experiment) the presentation in comparison to their levels before the presentation (baseline). There is a clear difference between the baseline and experiment showing an increase in levels and subjective rating scale scores. Although the results were not statistically significant for any of the variables, it still shows that there is an increase. These results are consistent with research that was conducted on “cardiovascular and neuroendocrine adjustments to public speaking and mental arithmetic stressors” by al’Absi.

The results of this study were similar to the past research as both of the research papers explained that there was an increase in systolic and diastolic pressure, heart rate in response to the tasks that the participants had to complete. Another study had been conducted which was similar to results of this study. The study examined endocrine and automatic reactivity in response to repeated exposure to stress throughout the use of VR (Virtual Reality). Results displayed an increase of 88% compared to the baseline and an increase of HR (Heart Rate) by up to 42% between trials. Although the results support our aim and hypothesis, there were some limitations to this study. There was only 135 of the 254 eligible participants that took part in the research so it is hard to generalise. Also, as stress is subjective to each individual, people participating may not find public speaking a stressful situation and results could be affected. Sex differences may also be another factor that could affect the results. As a study reported that males have a males between the ages of 18-22 have higher baseline levels of cortisol.

Therefore these could affect the results for levels of cortisol between Baseline and experimental making them higher than what it may actually be. In conclusion, the study was aimed to examine the effect of stress (public speaking) on subjective, cardiovascular and hormonal responses. The results from the study showed that all the variables that were tested had a significant change between the baseline and experimental, except for diastolic blood pressure. We can support hypothesis that students who participated in public speaking would display higher cardiovascular response (blood pressure and heart rate), increased endocrine response (cortisol levels in saliva) and higher subjective levels of stress after (experiment) the presentation in comparison to their levels before the presentation (baseline). However, due to some limitations of the study, we are unable to generalise for the population and further studies would need to be conducted before any generalisations can be made.